Fine particulate matter aggravates intestinal and brain injury and affects bacterial community structure of intestine and feces in Alzheimer's disease transgenic mice

Fine particulate matter (PM2.5) was a risk factor for neurological disorders when emerging studies revealed that PM2.5 affected the bacterial community structure of gut in Alzheimer's disease (AD) patients. The purpose of this study was to explore the effects of PM2.5 on intestinal and brain injury and on bacterial community structure in the intestine and feces of APP/PS1 transgenic mice exposed to PM2.5 for eight weeks with a real-world whole-body inhalation exposure system in Taiyuan, China. The brain and intestinal tissues were collected to evaluate histopathological changes by HE staining. TNF-α and IL-6 levels in intestines, brains, and serums, and Aβ-42 levels in brains were detected. Intestinal and fecal samples were subjected to 16S rRNA gene sequencing. Results showed that PM2.5 significantly aggravated the pathological injury in intestines and brains in AD mice with elevated pro-inflammatory cytokine levels. The estimators of Shannon, Simpson, Chao1, and ACE indexes reflected the diversity and richness of the bacterial community. Compared with the FA-WT group, the FA-AD group had lower diversity and richness when the PM2.5-AD group had the highest ones. PCA and NMDS revealed the specific influence of PM2.5 on the bacterial community of intestine and feces because that the PM2.5-FA and PM2.5-AD group clumped visibly closer than the other groups in both bacterial communities of intestine and feces. The KEGG pathway analysis predicted the vital functional genes and metabolic pathways in the bacterial community of PM2.5-AD mice. This study indicated the histopathological changes and inflammation in the intestine and brain were seriously caused in PM2.5-AD mice when the α-diversity of the bacterial community in intestine and feces was visibly changed.